As IC devices become more highly integrated and gate lengths of field effect transistors (FETs) are reduced, efforts to develop a device including a FinFET having a channel of a three-dimensional (3D) structure have been made to overcome limitations of characteristics of a device having a planar metal oxide semiconductor FET (MOSFET). In addition, efforts to improve characteristics related to operation speed, power consumption, and economic efficiency have been made to improve the overall operation stability of transistors of IC devices.